The doctors said they believed poisoning was an
extremely unlikely cause of his death, but that laboratory tests still needed to be carried out. Tissue samples are to be sent to London and it may be another month before results are known.

However family members still hold the military responsible for his death for holding him in detention for so long.

The findings - by a team drawn from the US, the UK and Canada - were announced a short time after the burial of Chief Abiola in the garden of his home, mourned by hundreds of supporters and family
members.

There were chaotic scenes as people tried to get a last glimpse of his body, which was lowered into the grave in a simple white shroud.

Much of the crowd had poured into the Abiola
compound in Lagos shortly before the burial took
place, when the security forces withdrew at the request of the family.

But many other mourners were kept away from the area by a security cordon.

Chief Abiola: died aged 60

The presence of armed riot police and soldiers had angered radical Abiola supporters, who considered it a provocation.

Chief Abiola's son Kola had appealed to the crowds not to allow violence during the funeral.

The body had been released to the family a few hours earlier after the completion of the post mortem examination.

BBC Lagos correspondent Hilary Andersson says this is a sad day
for Nigeria, which has lost a man who symbolised hopes of democracy for a nation
which has been ruled by the military off and on for the last 30 years.

Chief Abiola died on Tuesday, just as it seemed he was about to be released after four years in detention.

He collapsed while meeting a US delegation in Nigeria to discuss the transition to civilian rule and died a short time later in hospital.

Riots in south-west

Earlier on Saturday, several people were injured in riots in the south-western town of Ibadan, which has a large community from the north of Nigeria.

People in the south-west, where Chief Abiola came from, are furious that he died while still in detention ordered by military rulers who come from the north.

The latest trouble follows two days of rioting in Lagos and Abeokuta, his home town. Up to 60 people are reported to have died during the violence.

Chief Abiola was widely believed to have won a presidential election campaign in 1993, which was annulled by the military. He was jailed the following year when he declared himself president.